Process for producing alcohols from synthesis gas

ABSTRACT

A process for making alcohols comprising contacting a mixture of hydrogen and carbon monoxide with a catalyst comprising: 
     (1) as a first component, at least one element selected from the group consisting of molybdenum and tungsten in free or combined form; 
     (2) as a second component, at least one element selected from the group consisting of iron, cobalt and nickel in free or combined form; 
     (3) as a third component, a promoter comprising an alkali or alkaline earth element in free or combined form; and optionally 
     (4) as a fourth component, a support; 
     to form an alcohol fraction boiling in the range of motor gasoline in at least 20 percent CO 2  free carbon selectivity.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 636,000 filed July 30,1984, now abandoned.

FIELD OF THE INVENTION

This invention relates to a Fischer-Tropsch process for making alcoholsand describes the catalyst composition and conditions of the process.

BACKGROUND OF THE INVENTION

Almost as old as the Fischer-Tropsch process for making hydrocarbons isthe Fischer-Tropsch process for making alcohols. The reaction is carriedout by passing a mixture of carbon monoxide and hydrogen over a catalystfor the hydrogenation of the carbon monoxide. A typical review articleis R. B. Anderson et al., Industrial and Engineering Chemistry, Vol. 44,No. 10, pp. 2418-2424. This paper lists a number of catalysts containingzinc, copper, chromium, manganese, thorium, iron occasionally promotedwith alkali or other materials for making various alcohols The authorsstate that ethyl alcohol is a major constituent, the yield of methanolis usually very small and a tentative summary of factors favoring theproduction of alcohols are high pressure, low temperature, high spacevelocity, high recycle ratio and carbon monoxide-rich synthesis gas.

Molybdenum is known to be catalytic for the Fischer-Tropsch process andis taught in U.S. Pat. Nos. 4,151,190 and 4,199,522 which areincorporated herein by reference. The references describe some of theherein used catalysts but do not teach that the catalyst is useful formaking commercially significant quantities of alcohols.

U.S. Pat. No. 2,490,488 discloses that molybdenum sulfide methanationcatalysts acquire Fischer-Tropsch activity when promoted with analkaline compound of an alkali metal. The example of the invention showsa 30 percent selectivity to C₃ + hydrocarbons and oxygenates. Of this 30percent, no more than 44 percent boils near or above 65° C. the boilingpoint of methanol. Accordingly the maximum possible alcohol selectivityis no more than 13.2 percent (44 percent of 30 percent).

U.S. Pat. No. 2,539,414 describes a Fischer-Tropsch process withmolybdenum carbide catalysts. It teaches that the catalyst may be usedto form oxygenates and at column 3, lines 66-71 teaches that one mightget alcohols or hydrocarbons by varying the conditions.

G. T. Morgan et al., J. Soc. Chem. Ind., Vol. 51, 1932 January 8, pp.1T-7T, describe a process for making alcohols with chromium/manganeseoxide catalysts promoted with alkali.

A number of references teach production of alcohols using rhodiumcatalysts. Some of these contain molybdenum as an optional ingredient.U.S. Pat. No. 4,014,913 discloses a catalyst containing rhodium andthorium or uranium and iron or molybdenum or tungsten for the productionof ethanol. U.S. Pat. No. 4,096,164 discloses the use of rhodium incombination with molybdenum or tungsten. Example A discloses that use ofa molybdenum-on-silica catalyst yielded 4.4 percent oxygenates.

EPO application No. 81- 33,212 (Chemical Abstracts 96:51,800a) disclosesa similar process using rhodium in combination with one or more of along list of metals which includes molybdenum.

EPO application No. 79-5,492 (Chemical Abstracts 92:166,257b), Hardmanet al., discloses the production of alcohols using a 4-componentcatalyst. The first component is copper, the second is thorium, thethird an alkali metal promoter and the fourth a long list of metals oneof which is molybdenum. Chemical Abstracts 96:106,913x, Diffenbach etal., disclose a nitrided iron catalyst which is promoted with molybdenumfor making alcohols from synthesis gas.

All of the aforementioned references are hereby incorporated byreference.

U.S. patent application Ser. No. 476,674, filed Mar. 18, 1983 and U.S.patent application Ser. No. 622,029, filed June 18, 1984, which areincorporated herein by reference disclose a process for making mixedalcohols by contacting hydrogen and carbon monoxide with a catalystcontaining, molybdenum, tungsten or rhenium in combination with analkali(ne earth) promoter and optionally a support. The Applicantsdisclose that other metals such as iron, nickel or cobalt may also becombined with their catalyst but do not teach advantageous results forthe combination.

While this process is an advance over the art it would be moreadvantageous if it were possible to decrease the percentage of methanolin the mixed alcohols made. Methanol has been blamed for difficultieswhen blended into motor gasolines. Accordingly there is some advantageto varying or minimizing the ratio of C₁ to C₂ + alcohols in the mixedalcohols made by the processes of Ser. No. 476,674 and Ser. No. 622,029.

U.S. application, Ser. No. 635,999, filed on even date herewith, whichis incorporated herein by reference discloses a method for adjusting theratio of C₁ to C₂ + alcohols in the processes of Ser. No. 476,674 andSer. No 622,029 by adjusting the addition rate of a sulfur releasingsubstance to the H₂ /CO feed. Increasing the sulfur level decreases theC₁ to C₂ + alcohols ratio. Concurrently, however, increasing the sulfurin the feed also decreases the activity or weight of alcohols per unitweight of catalyst per unit of time. It would be more desirable to lowerthe C₁ to C₂ + ratio without lowering the activity of the catalyst. Useof sulfur releasing substances also requires that sulfur be removed fromthe mixed alcohols product.

To make a commercially significant alcohol process, one must use acatalyst and conditions which are highly efficient. To be efficient thecatalyst must yield a high ratio of mass of product per given mass ofcatalyst in a given period of time. The catalyst must be stable andactive for long periods of time between regenerations. This may beparticularly difficult to accomplish when the H₂ /CO ratio of the feedgas is low, such as less than 2 to 1. Ideally the catalyst will behighly selective to a commercial product to avoid purification orremoval and disposal of by-products and to avoid separation into two ormore product streams.

When the mixed alcohols product is to be used as a fuel replacement or afuel additive it may be desirable that the ratio of C₁ to C₂ + alcoholsbe no greater than a certain amount. As used in this Application, theratio of C₁ to C₂ + alcohols means the weight ratio of methanol tohigher alcohols such as ethanol, propanols, butanols, etc., taken as awhole. This number may be calculated by determining the weight fractionof methanol in the mixed alcohols. When the weight fraction of methanolis x, the ratio of C₁ to C₂ + alcohols is x/1-x. Since C₂ + alcohols, inits broadest definition refers to alcohols which are not detected byconventional analytical techniques, a more meaningful approximation ofthe C₁ to C₂ + ratio of methanol to higher alcohols includes only the C₂-C₅ alcohols in the definition of C₂ + alcohols. Alcohols bound asesters or ethers are not included in either the C₁ or C₂ + numbers.

OBJECTS OF THE INVENTION

It is an object of this invention to prepare alcohols from H₂ /COsynthesis gas. It is a preferred object of this invention to make a highyield of alcohols with a catalyst which is selective to alcohols boilingin the range of motor gasoline and that is stable, particularly at lowH₂ /CO ratios, and active over long periods of time. It is a mostpreferred object of this invention to obtain a mixed alcohol fractionwith a lower C₁ to C₂ + alcohols ratio than obtainable with a straightmolybdenum catalyst without lowering the activity of the catalyst andwithout increasing the sulfur level in the product stream.

SUMMARY OF THE INVENTION

One or more of the objects of the invention may be effected by a processfor making alcohols comprising contacting a mixture of hydrogen andcarbon monoxide with a catalyst comprising:

(1) as a first component at least one element selected from the groupconsisting of molybdenum and tungsten in free or combined form;

(2) as a second component at least one element selected from the groupconsisting of iron, cobalt and nickel in free or combined form;

(3) as a third component, a promoter comprising an alkali or alkalineearth element in free or combined form; and optionally as a fourthcomponent

(4) a support;

to form an alcohol fraction boiling in the range of motor gasoline in atleast 20 percent CO₂ free carbon selectivity.

It is a feature of this invention, that high yields and selectivity maybe obtained without the use of rhodium, copper, ruthenium or zinc. Anadvantage of the invention is that high production rates may be obtainedat high selectivities. Under preferred conditions, these catalysts mayyield high C₁ -C₅ alcohol productivity. Up to about 1.4 weight units C₁-C₅ alcohol/hr/weight unit of catalyst may be achieved. With cobalt,iron or nickel added to the catalyst the ratio of C₁ to C₂ -C₅ alcoholsmay be considerably lower than for the same catalyst without the iron,nickel or cobalt, while still retaining the high catalyst activity andlow sulfur level mixed alcohol fraction. Because of the highselectivity, complex purification steps may be avoided and the alcoholproduct may have a low acid content and have a high octane blendingvalue. This may permit blending into motor fuels without elaborateprocessing. In addition, contrary to what is experienced with amolybdenum catalyst as one increases the temperature the ratio of C₁ toC₂ -C₅ alcohols may stay the same or may even decrease.

DETAILED DESCRIPTION OF THE INVENTION

The hydrogen and carbon monoxide required for this process can beobtained by methods known in the art. Examples are gasification ofhydrocarbonaceous materials such as coal, high specific gravity oils, ornatural gas; as a by-product of partial combustion cracking ofhydrocarbons; by steam reforming of liquid or gaseous hydrocarbons;through the water-gas shift reaction; or some combination of these. Thetwo components may also be generated separately and combined for thesubject reaction. The molar ratio of hydrogen to carbon monoxide in thefeed gas which contacts the catalyst ranges generally from about 0.25 toabout 100, preferably from about 0.5 to about 5 and most preferably fromabout 0.7 to about 3. A most preferred range of from about 0.7 to about1.2 holds for unsupported Co/MoS₃ catalysts.

Generally, the selectivity to alcohols is dependent on the pressure. Inthe normal operating ranges, the higher the pressure at a giventemperature, the more selective the process will be to alcohols. Theminimum contemplated pressure is about 500 psig (3.55 MPa). Thepreferred minimum is about 750 psig (5.27 MPa) with about 1,000 psig(7.00 MPa) being a more preferred minimum. While about 1,500 psig (10.45MPa) to about 4,000 psig (27.7 MPa) is the most desirable range, higherpressures may be used and are limited primarily by cost of the highpressure vessels and compressors needed to carry out the higher pressurereactions. A typical maximum is about 10,000 psig (69.1 MPa) with about5,000 psig (34.6 MPa) a more preferred maximum.

The selectivity to alcohols is also a function of temperature and isinterrelated with the pressure function. The minimum temperature used isgoverned by productivity considerations and the fact that attemperatures below about 200° C. volatile catalytic metal carbonyls mayform. Accordingly, the minimum temperature is generally around 200° C.

For a given catalyst, at a constant pressure, as the temperatureincreases, the selectivity to alcohols decreases. A preferred maximumtemperature is about 400° C. A more preferred maximum is about 350° C.However, the most preferred range of operation is from about 240° C. toabout 325° C.

The H₂ /CO gas hourly space velocity (GHSV) is a measure of the volumeof hydrogen plus carbon monoxide gas at standard temperature andpressure passing a given volume of catalyst in an hour's time. This mayrange from about 100 to about 20,000 hour⁻¹ and preferably from about2,000 to about 5,000 hour⁻¹. Selectivity to the alcohols generallyincreases as the space velocity increases. However, conversion of carbonmonoxide decreases as space velocity increases.

Preferably at least a portion of the unconverted hydrogen and carbonmonoxide in the effluent gas from the reaction, more preferably afterremoval of product alcohols, water and carbon dioxide formed and evenmore preferably any hydrocarbons formed, may be recycled to thereaction. The amount of recycle is expressed as the recycle ratio whichis the ratio of moles of gases in the recycle stream to the moles ofgases in the fresh feed stream. A recycle ratio of zero is within thescope of the invention with at least some recycle preferred. A recycleratio of at least about one is more preferred and at least about threeis most preferred.

With preferred catalysts and under preferred conditions of temperatures,pressures, H₂ /CO ratio, GHSV and recycle ratio, about 0.1 weight unitsof alcohols or more per hour may be formed per weight unit of catalyst.Under the more preferred conditions of about 310° C., 1500 psig (10.45MPa), 3800 hour⁻¹ and a H₂ /CO ratio of about 1:1, with a 2Mo/Cocatalyst, about 0.3 weight units of alcohol or more per hour per weightunit of catalyst may be obtained. Under the most preferred conditions ofabout 340° C., 3000 psig (20.9 MPa), a GHSV of 13,000 and a H₂ /CO ratioof 1.1; with a 2Mo/Co catalyst about 1.4 weight units of alcohols ormore per hour per weight unit of catalyst may be obtained.

Under preferred conditions, alcohols may be obtained in about an 85percent CO₂ free carbon selectivity. The CO₂ free carbon selectivity isdefined as 100 times the moles of carbon present in a product fractiondivided by the total moles of carbon in all products which are not CO₂or unconverted feed. For example, if one mole of ethanol is found in thealcohol fraction, this is counted as 2 moles of carbon. If 4 moles of COhad been converted to products other than CO₂, the one mole of ethanolwould result in ethanol being yielded at 50 carbon mole percent. Carbondioxide and water are not counted as products in this calculation.

The first component of the catalyst preferably consists essentially ofat least one element selected from the group consisting of molybdenumand tungsten in free or combined form. Molybdenum is preferred.

The first component of the catalyst may be present in the catalyst in"free or combined form" which means that it may be present as a metal,an alloy or a compound of the element. Representative compounds includethe sulfides, carbides, oxides, halides, nitrides, borides, salicylides,oxyhalides, carboxylates such as acetates, acetyl acetonates, oxalates,etc., carbonyls, and the like. Representative compounds also include theelements in anionic form such as molybdates, phosphomolybdates,tungstates, phosphotungstates, and the like, and include the alkali,alkaline earth, rare earth and actinide series salts of these anions.The sulfides, carbonyls, carbides and oxides are preferred with thesulfides being most preferred.

The molybdenum or tungsten may be present in an amount based on theweight of the total catalyst of at least about two percent, preferablyat least about 5 percent with an upper limit of about 70 percent andpreferably about 30 percent of the total catalyst.

The first and second components may be generally present as the sulfide.It is not necessary for the practice of this invention that anyparticular stoichiometric sulfide be present, only that the first andsecond components may be present in combination with sulfur. Some of thefirst or second component may be present in combination with otherelements such as oxygen or as oxysulfides.

The second component of the catalyst preferably consists essentially ofat least one element selected from the group consisting of iron, cobaltor nickel in free or combined form. Cobalt and nickel are preferred.Because of the possiblity of the formation of nickel tetracarbonyl,cobalt is most preferred.

The second component of the catalyst may be present in the catalyst in"free or combined form" which means that it may be present as a metal,an alloy or a compound of the element. Representative compounds includethe sulfides, carbides, oxides, halides, nitrides, borides, salicylides,oxyhalides, carboxylates such as acetates, acetylacetonates, oxalates,etc., carbonyls, and the like. Representative compounds also include theelements combined with first component elements in anionic form such asiron, cobalt or nickel molybdates, phosphomolybdates, tungstates,phosphotungstates, and the like. The sulfides, carbonyls, carbides andoxides are preferred with the sulfide being most preferred.

The iron, cobalt or nickel or mixtures thereof may be present in anamount based on the weight of the total catalyst of at least about twopercent, preferably at least about 5 percent with an upper limit ofabout 70 percent and preferably about 30 percent of the total catalyst.

The first and second components may be present in the finished catalystin an atomic ratio of about 1:10 to about 10:1. Preferably the first andsecond components are present in a ratio of from about 1:4 to about 4:1.With a coprecipitated Mo/Co sulfide catalyst an atomic ratio of Mo/Co ofabout 2:1 yields about a 1:5 weight ratio of methanol to C₂ -C₅ alcoholsand an atomic ratio of about 3:1 yields a weight ratio of about 1:3methanol to C₂ -C₅ alcohols.

The third component which is a promoter may consist essentially of oneor more alkali elements or alkaline earth elements in free or combinedform. Alkali elements include lithium, sodium, potassium, rubidium andcesium. Alkaline earth elements include: beryllium, magnesium, calcium,strontium and barium. Alkali elements and in particular, cesium andpotassium, are preferred. Potassium is most preferred.

The promoter may be present in free or combined form as a metal, oxide,hydroxide, carbonate, sulfide or as a salt or a combination of these.The alkaline promoter is preferably present at a level sufficient torender the supported catalyst or the bulk catalyst more basic. Thepromoter is generally present in an amount of at least about 0.05 weightpercent as a free element in the finished catalyst. Preferably it ispresent in an amount of at least about 0.5 percent and most preferablyat least 2.0 percent. Large amounts up to about 30 percent of thepromoter may be present. Preferably the promoter is present at less than20 percent.

The promoter may be added as an ingredient to the other components or tothe support or may be part of one of the other components such as sodiumor potassium molybdate or as an integral part of the support. Forexample, carbon supports prepared from coconut shells often containsmall amounts of alkali metal oxides or hydroxides or the support maycontain a substantial amount of the promoter such as when the support ismagnesia.

A fourth optional component of the catalyst is a support which mayassume any physical form such as pellets, granules, beads, extrudates,etc. The supports may be coprecipitated with the active metal species,or the support in powder form may be treated with the active metalspecies and then used as is or formed into the aforementioned shapes, orthe support may be formed into the aforementioned shapes and thentreated with the active catalytic species.

The first three components may be dispersed on the support by methodsknown in the art. Examples include: impregnation from solution followedby conversion to the active species, vapor deposition, intimate physicalmixing, sulfiding of other first or second component species,precipitation of sulfides in the presence of the support and the like.One or more of these methods may be used.

One alternative method of placing the first three components on thesupport is known as the incipient wetness technique. Water- orsolvent-soluble salts of the metals to be dispersed on the support arechosen. The soluble salts which may be a single salt or more than onesalt are dissolved in a quantity of solvent which may be aqueous,nonaqueous or a mixed solvent. A sufficient quantity of the resultingsolution is added to the support in an amount no more than will becompletely absorbed by the support. The solvent is then evaporated toleave the salt dispersed on the support. Depending on the solubility ofthe salt chosen and on the quantity of the element desired to bedispersed on the support, this process may be performed once or severaltimes. Impregnations with two or more species may be performed bycodissolving them in the solvent or by adding them separately indifferent quantities or types of solvent. If the species loaded on thesupport is not the desired one, the loaded support may be treated toconvert it to the desired species. For example, oxides may be reduced,with reducing agents such as hydrogen; salts may be decomposed forexample by heating, for example, the decomposition of (NH₄)₂ MoS₄ orMoS₃ to MoS₂ ; or one species may be converted to another by contactwith a chemical agent, for example sulfiding. A catalyst may be sulfidedby contact with a sulfur-containing agent such as H.sub. 2 S.

Preferred methods of placing the first or second components on a supportinclude, for example, impregnation with (NH₄)₂ MoS₄ followed bydecomposition with heat; precipitation of sulfides of the first and/orsecond components in contact with the support. Placing of the sulfidedfirst and second components on a support is preferably followed bytreatment with H₂ at elevated temperatures, usually with 20-50 ppm H₂ Spresent.

Exemplary support materials include: the aluminas, basic oxides, thesilicas, carbons, or suitable solid compounds of magnesium, calcium,strontium, barium, scandium, yttrium, lanthanum and the rare earths,titanium, zirconium, hafnium, vanadium, niobium, tantalum, thorium,uranium, and zinc. Oxides are exemplary compounds. Preferably thesupports are neutral or basic or may be rendered neutral or basic byaddition of the alkaline promoters. The aluminas include the alpha,gamma, and eta types. The silicas include for example, silica gel,diatomaceous earth, and crystalline silicates.

The carbon supports, which are preferred supports, include activatedcarbons such as those prepared from coals and coal-like materials,petroleum-derived carbons and animal- and vegetable-derived carbons.Preferably the carbon support will have a surface area of 1-1500 m² /g,more preferably 10-1000 m² /g and most preferably 100-500 m² /g asmeasured by the BET nitrogen test. Preferably, micropores (<Å (<2 nm))are minimized and at least twenty percent of the volume of the porescomprises pores having a diameter of from about 20 Å to about 600 Å(2-60 nm). Examples include coconut shell charcoal, coals, petroleumcokes, carbons formed by pyrolyzing materials such as vinylidenechloride polymer beads, coal, petroleum coke, lignite, bones, wood,lignin, nut shells, petroleum residues, charcoals, etc.

Based upon the weight of the total catalyst, the support when presentgenerally comprises at least about 20 percent of the catalyst andgenerally not more than about 96 percent of the catalyst. Preferably thesupport comprises at least about 50 weight percent and most preferablyat least about 70 weight percent of the catalyst.

For several reasons the preferred form of the catalyst is theagglomerated sulfide. Certain forms of cobalt/molybdenum sulfide aremore preferred. Most preferred is agglomerated, cobalt/molybdenumsulfide in which the cobalt and molybdenum sulfides are coprecipitated.

Methods for making sulfide catalysts are disclosed generally at pages23-34 of Sulfide Catalysts Their Properties and Applications, O. Weisserand S. Landa, Pergamon Press, New York, 1973, the whole which isincorporated herein by reference.

Sulfide catalysts may be made by precipitating iron, cobalt or nickelsulfide in the presence of ammonium tetrathiomolybdate or otherthiomolybdates, or thiotungstates and thereafter thermally treating themixture to convert the thiomolybdate or thiotungstate salt to thesulfide; or as disclosed in U.S. Pat. No. 4,243,553 and U.S. Pat. No.4,243,554 which are hereby incorporated by reference; or from purchasedactive combined first and second component sulfides.

Cobalt and molybdenum may be impregnated as salts on a support, thencalcined to the oxide and then sulfided with H₂ S as taught in GB patentpublication No. 2,065,491 which is incorporated herein by reference. Acobalt/molybdenum sulfide may also be precipitated directly on to asupport, but the unsupported cobalt/molybdenum sulfide is preferred.Other combinations of first and second component sulfides may besimilarly made.

An unsupported catalyst preferably has a surface area of at least 10 m²/g and more preferably more than 20 m² /g as measured by the BETnitrogen surface area test.

A preferred method of making a cobalt/molybdenum sulfide or other firstand second component sulfide is by adding solutions of ammoniumtetrathiomolybdate or other equivalent salt and a cobalt or nickel saltsuch as the acetate more or less simultaneously to 30 percent aceticacid. This results in the coprecipitation of cobalt/molybdenum sulfide.By varying the ratios of cobalt and molybdenum or other salts in thesolutions one may vary the ratio of cobalt and molybenum or otherelements in the sulfide catalyst. The cobalt/molybdenum sulfide or othersulfide may then be separated from the solvent, dried and blended with athird component promoter such as K₂ CO₃ and agglomerating agents and/orpelleting lubricants, then pelleted and used as the catalyst in theprocess.

The alkali or alkaline earth promoter may be added to the activecatalytic elements prior to, during or after the formation of thesulfide by physical mixing or solution impregnation. The active metalsulfide may then be combined with binders such as bentonite clay, and/orpelleting lubricants such as Sterotex® and formed into shapes for use asa catalyst.

The finished catalyst may be used in a fixed bed, moving bed, fluid bed,ebullated bed or a graded bed wherein concentration and/or activity ofthe catalyst varies from inlet to outlet in similar manner to knowncatalysts. The catalyst may be used in powdered form or may be formedinto shapes with or without a binder.

Catalysts of the invention preferably contain less than 25 weightpercent, based on the total weight of carbon oxide hydrogenation activemetals, of other carbon oxide hydrogenation active metals and morepreferably less than 20 weight percent and most preferably less than 2weight percent. The inventive catalyst may be essentially free of othercarbon oxide hydrogenating components. By essentially free it is meantthat other carbon oxide hydrogenating components do not significantlyalter the character or quantity of the alcohol fraction. For example, asignificent change would be a five percent change in the amount of thealcohol fraction or a five percent change in the percentage of anyalcohol in the alcohol fraction.

Carbon oxide hydrogenating components present in thus limited quantitiesor excluded are preferably those that contain chromium, manganese,copper, zinc, ruthenium and rhodium. More preferably, in addition to theabove-mentioned components, those that contain: halogen, titanium,vanadium, cerium, thorium, uranium, iridium, palladium, platinum, silverand cadmium are excluded.

Under preferred conditions the catalyst is stable for long periods oftime and under ideal conditions may be stable and active for as many as6000 hours or more. Activity and selectivity are preferablysubstantially retained after 700 hours of operation, more preferablyafter 2000 hours and most preferably after 4000 hours operation. In thecase of reduced oxide catalysts, declines in activity and selectivitymay generally be regenerated by reduction with hydrogen after which thecatalyst may regain most of its original activity and be used foranother long period of time before regenerating again.

The catalysts are generally not adversely affected by up to 100 ppmsulfur in the H₂ /CO feed. However, no advantage is realized by thepresence of sulfur, and generally sulfur must be removed from the mixedalcohols fraction. Accordingly, low sulfur levels in the feed arepreferred.

At the conditions described above, the process yields substantialquantities of alcohols. Under preferred conditions, the weight units perhour of alcohols boiling in the range of motor gasoline per weight unitof catalyst may exceed 0.2. Under certain conditions, it may exceed 1.0and may reach 1.4.

The alcohol fraction formed at greater than a 20 percent CO₂ free carbonselectivity boils in the motor gasoline range. The minimum boiling purealcohol is methanol at 64.7° C. ASTM D-439 calls for a 225° C. endpointfor automotive gasoline. Accordingly the alcohol fraction formed atgreater than a 20 percent CO₂ free carbon selectivity may boil in therange of from about 60° C. to about 225° C. when distilled by ASTM D-86.Other alcohols may boil outside this range but preferably do not. It isnot necessary that the entire liquid product boil in this range, but itis preferred. It is not necessary that the alcohol fraction meet all thedistillation specifications for motor gasolines--only that it boilwithin the broad range of motor gasolines. For example, it need not bewithin 50 percent evaporated limits as set by ASTM D-439. Only 20 carbonmole percent of the total CO₂ free product must be alcohols that boil inthis range. The alcohol fraction formed may be used as a motor fuelblending stock. Preferably, the alcohol fraction formed will have aresearch octane blending value in motor gasoline of greater than about100, more preferaby greater than about 110 and most preferably greaterthan about 120.

Preferably, a C₁ -C₈ alcohol fraction is formed in at least about 20percent CO₂ free carbon selectivity and most preferably a C₁ -C₅ alcoholfraction is formed in at least about 20 percent CO₂ free carbonselectivity.

The C₁ -C₅ alcohol fraction may contain methanol, ethanol, 1-propanol,1-butanol, 2-methyl-1-propanol, 1-pentanol, 2-methyl-1-butanol, butdoesn't generally contain substantial tertiary alcohols. In addition tothese named alcohols the C₁ -C₈ alcohol fraction may contain the C₆ -C₈alcohols wherein the hydroxyl group may be attached to a carbon which isattached to one or two other carbon atoms.

The process for making mixed alcohols may yield a lower ratio of C₁ toC₂ -C₅ alcohols in the alcohol fraction with the combination of thefirst, second and third components and optionally the fourth componentlisted above than with a catalyst containing the same first, third andoptional fourth component but not the second component. With just thefirst, third and optional fourth component, and absent addition of asulfur, releasing substance a typical C₁ to C₂ -C₅ weight ratio may be1.1 or more. With the catalyst of the invention the C₁ to C₂ -C₅ weightratio may be less than one, preferably is less than about 0.8, morepreferably less than about 0.5 and most preferably less than about 0.4and can even be about 0.25 or lower.

Primarily the C₂ -C₅ alcohol that increases is ethanol. The weightpercentage of ethanol made without the second component in the catalystis typically less than 25 percent of the total C₁ -C₅ alcohols. In thepresence of an iron-, cobalt- or nickel-containing catalyst of the samecharacter otherwise, the ethanol may be greater than 25 weight percent,preferably greater than 30 weight percent and most preferably greaterthan 40 weight percent of the C₁ -C₅ alcohol fraction.

The catalysts of the invention preferably contain the first componentand second component in an atomic ratio of less than about 5:1.Preferably, the atomic ratio is less than 3:1 and most preferably about2:1 or less.

Coprecipitated cobalt/molybdenum sulfide is the preferred combination ofthe first and second components. The sulfur content may or may not bestoichiometric as there are many sulfides of these two metals.

Under preferred conditions, the amount of water formed is substantiallyless than the amount of alcohols formed. Typically there is less than 20weight percent and preferably less than 10 weight percent water based onthe quantity of alcohol. This water may be removed by known techniquesif the alcohol fraction is to be used as a motor fuel additive. If thewater content is about two weight percent or less based on alcohols, thewater may advantageously be removed by absorption on molecular sieves.At higher water contents one may use a water gas shift drying step asdisclosed in British patent publication Nos. 2,076,015 and 2,076,423; orU.S. patent application Ser. No. 508,625, filed June 28, 1983. Thesereferences are hereby incorporated herein by reference. A water gasshift catalyst tolerant to sulfur, and alcohol catalyst carry overshould be used in the drying step. Halder Topsoe SSK is exemplary.

The product mixture, as formed under preferred conditions, contains onlysmall portions of other oxygenated compounds besides alcohols. Theseother compounds may not be deleterious to using the product, as is, inmotor fuels.

In all cases, the alcohol fraction is formed in at least about 20percent CO₂ free carbon selectivity. Preferably the alcohol fraction isformed in at least about 30 percent CO₂ free carbon selectivity, morepreferably greater than about 50 percent and ideally can be greater thanabout 70 percent.

Preferably the co-products formed with the alcohol fraction areprimarily gaseous products. That is C₁ -C₄ hydrocarbons. Byhydrocarbons, it is meant that heteroatoms such as oxygen, sulfur andnitrogen are not present in the molecule. Preferably C₅ + hydrocarbonsare coproduced at less than about 20 percent CO₂ free carbonselectivity, more preferably at less than 10 percent and most preferablyat less than 5 percent. Lower amounts of normally liquid hydrocarbonsmake the normally liquid alcohols easier to separate from by-products.

Generally, alcohol selectivity may be increased by increasing pressure,space velocity, product gas recycle ratio and by decreasing H₂ /CO feedratio and temperature.

CATALYSTS Comparison A

A solution of 180 g of (NH₄)₆ Mo₇ O₂₄ 4H₂ O in 500 cm³ of watercontaining 100 cm³ of concentrated NH₄ OH reacts with a small excess of(NH₄)₂ S (about 1300 cm³ of 22 percent (NH₄)₂ S in water). The reactionmixture is stirred at 60° C. for one hour and evaporated to dryness at60° C.-70° C. A portion of the resulting (NH₄)₂ MoS₄ is calcined at 500°C. for one hour in an inert atmosphere such as nitrogen to form MoS₂.The resulting MoS₂ powder (6.6 g) is mixed with 2.0 g of bentonite clay,1.0 g of K₂ CO₃ and 0.4 g of a pelleting lubricant (Sterotex®) bygrinding in a mortar and pestle. The product is used to make alcohols inthe unpelleted powder state. No pretreatment of the catalyst isperformed.

EXAMPLE 1

A 10.0-g portion of the MoS₂ from Comparison A is mixed in a mortar andpestle with 8.4 g Co(CH₃ CO₂)₂ 4H₂ O (cobalt acetate) and watersufficient to yield a thick paste. The paste is dried at 60° C. andcalcined at 500° C. for one hour in an inert gas such as nitrogen togive a black powder with a Mo/Co atomic ratio of about 3:1.

Similar to Comparison A, 6.6 g of this powder are mixed with 2.0 gbentonite clay, 1.0 g of K₂ CO₃ and 0.4 g of Sterotex® in a mortar andpestle. This catalyst is used in unpelleted powder form and is notpretreated.

EXAMPLE 2

A coprecipitated cobalt/molybdenum sulfide is prepared with a Mo/Coatomic ratio of about 2:1. Fifteen grams of (NH₄)₆ Mo₇ O₂₄ 4H₂ O (0.085moles Mo) is dissolved in 106 cm³ of 22 percent (NH₄)₂ S in water andstirred at 60° C. for one hour to form (NH₄)₂ MoS₄. A solution of 10.5 gof Co(CH₃ CO₂)₂ (0.042 mole Co) in 200 cm³ of water is prepared.

The two solutions are added simultaneously, dropwise to a stirredsolution of 30 percent aqueous acetic acid in a baffled flask at 50° C.over a one-hour period. After stirring for one additional hour thereaction mix is filtered and the filter cake dried at room temperatureand then calcined for one hour at 500° C. in an inert atmosphere such asnitrogen. Similar to Example 1, 6.6 g of the calcined cobalt/molybdenumsulfide is ground together with 2.0 g of bentonite clay, 1.0 g of K₂ CO₃and 0.4 g of Sterotex® lubricant in a mortar and pestle. This catalystis used in unpelleted, powder form without pretreatment.

EXAMPLE 3

This Example discloses the making of a coprecipitated cobalt/molybdenumsulfide with a Mo/Co atomic ratio of about 3:1.

The coprecipitated cobalt/molybdenum sulfide is prepared using the sameprocedure as Example 2 except that 7.1 g of Co(CH₃ CO₂)₂.4H₂ O (0.28moles Co) is used. This catalyst is used in unpelleted, powder formwithout pretreatment.

EXAMPLE 4

This Example discloses the use of a commercially available alkalizedmolybdenum/cobalt catalyst, Haldor Topsoe SSK, and available from HaldorTopsoe A/S of Denmark.

EXAMPLE 5

This Example discloses the use of an alkalized Mo/Ni sulfide having aMo/Ni atomic ratio of about 2:1.

Seventy-five grams (0.425 mole) of (NH₄)₆ Mo, O₂₄.H₂ O is dissolved in530 cm³ of 22 percent aqueous (NH₄)₂ S at 60° C.-70° C. with stirringfor one hour to give a solution of (NH₄)₂ MoS₄. A second solutioncontaining 53 g of nickel acetate (0.212 mole Ni) in 500 cm³ of water isprepared. These two solutions are added dropwise over a 40-minute periodto one liter of vigorously stirred 30 percent acetic acid. Afterstirring for one additional hour at 60° C., the resulting slurry isfiltered. The black filter cake is washed with water and dried overnightat 100° C. under nitrogen. The dry filter cake is calcined undernitrogen at 500° C. for one hour. Similarly to Example 1, 6.6 g of thecalcined Mo/Ni sulfide is ground with mortar and pestle with 2 g ofbentonite clay, 1 g of K₂ CO₃ and 0.4 g of Sterotex® pelletinglubricant. The catalyst is used in unpelleted powder form withoutpretreatment. Results are shown in the Table.

EXAMPLE 6

This Example discloses the use of a Mo/Fe sulfide made bycoprecipitation.

A barium acetate solution, prepared by dissolving 12.2 g (0.071 mole) ofBa(OH)₂ in 100 cm³ of water containing 10 cm³ of glacial acetic acid, ismixed with 100 cm³ of aqueous solution containing 19.7 g (0.071 mole) ofFeSO₄. The resulting precipitate was filtered off under nitrogen anddiscarded, leaving a solution of ferrous acetate. A solution of (NH₄)₂MoS₄ (0.142 mole) is prepared by dissolving 25 g of (NH₄)₆ Mo₇ O₂₄.4H₂ Oin 180 cm³ of 22 percent aqueous (NH₄)₂ S and stirring at 60° C. for onehour. The solutions of ferrous acetate and ammonium tetrathiomolybdateare added simultaneously over a 30-minute period to a vigorously stirredsolution of 75 cm³ of glacial acetic acid in 225 cm³ of water at 60° C.The resulting black slurry is stirred at 60° C. for one hour andfiltered. The black filter cake is washed, dried at 110° C. overnightunder nitrogen, and calcined at 500° C. under nitrogen for one hour. Thecalcined Mo/Fe sulfide is blended in a mortar and pestle with bentoniteclay, K₂ CO₃ and Sterotex® to give a formulation containing 66 percentMo/Fe sulfide, 20 percent clay, 10 percent K₂ CO₃ and 4 percentSterotex®. This catalyst (5 cm³) is combined with 5 cm³ of tabularalumina and loaded into the reactor.

Preparation of Alcohols

In the general method of these Examples, the reactor consists of aone-half inch (1.27 cm) stainless steel tube packed with catalyst. Thetotal volume of catalyst is about 6 cm³. Premixed hydrogen, carbonmonoxide, and nitrogen feed gases from cylinders are compressed andregulated at the pressures stated in the table. The feed gas mixturecontains hydrogen and carbon monoxide at the stated molar ratios andabout five percent by volume of nitrogen serving as an internalstandard. About 50 ppm of H₂ S is also present in the feed gas.

The mixed feed gas passes through the bed of activated carbon at roomtemperature to remove iron and other carbonyl containants. The feed gasthen passes at the stated hourly space velocities through the fixed bedreactor which is maintained at the stated reaction temperatures by anelectric air recirculated oven and which is held at 1500 psig (10.45MPa.) The reactor effluent passes through a gas liquid separator atambient temperature and the reaction pressure stated in series with adry ice trap at ambient pressure. Both gas and liquid phases areanalyzed to give the results in Table I.

                  TABLE I                                                         ______________________________________                                        Example    A      1      2     3    4    5    6                               ______________________________________                                        Temp. (°C.)                                                                        265    295    305   295 350   300  321                            H.sub.2 /CO (molar                                                                       1.04   0.98   0.98  0.98 1.02 1.03 1.04                            ratio)                                                                        GHSV (hr.sup.-1)                                                                         1200   2200   1300  1050 614  1330 1480                            CO Conver- 33.1   10.3   39.0  29.2 12.7 33.1 27.1                            sion (%)                                                                      Wt. Units CO                                                                             0.19   0.12   0.23  0.13 0.04 0.26 0.27                            converted per                                                                 wt. unit of                                                                   catalyst per hr                                                               CO.sub.2 pro-                                                                            31.3   18.6   33.5  31.3 40.1 32.9 36.9                            duced.sup.1 (%)                                                               Selectivities.sup.2 (%)                                                                  20.2   7.0    12.6  11.3 21.7 18.0 7.4                             Gas Phase                                                                     CH.sub.4                                                                      C.sub.2.sup.+                                                                 hydrocarbons                                                                             4.3    3.2    5.7   3.2  4.9  2.7  16.7                            Subtotal   24.5   10.2   18.2  14.5 26.6 20.7 24.1                            Liquid Phase                                                                  Methanol   32.3   37.8   16.1  22.7 17.7 15.2 6.9                             Ethanol    31.8   29.5   39.9  40.7 15.2 41.8 21.0                            Propanols  7.7    7.8    14.9  12.7 16.7 11.5 17.9                            Butanols   1.6    5.3    4.3   3.5  10.9 1.4  10.8                            Pentanols  0.2    2.4    0.5   1.2  5.0  1.5  7.1                             Subtotal   73.6   82.8   75.7  80.8 65.5 71.4 63.7                            Weight Ratio                                                                             1.13   1.24   0.39  0.57 0.60 0.39 0.19                            C.sub.1 /C.sub.2 -C.sub.5                                                     alcohols                                                                      Other oxygen-                                                                            1.9    7.0    6.0   4.7  7.9  7.9  12.2                            ates.sup.3 and                                                                hydrocarbons                                                                  H.sub.2 O.sup.4 (wt. %)                                                                  2.7    1.4    1.8   2.3  4.6  1.9  6.7                             ______________________________________                                         .sup.1 100 × moles of CO.sub.2 formed for each mole of CO converted     in the reactor.                                                               .sup.2 Selectivities, except for CO.sub.2, are based on carbon mole           selectivity on a CO.sub.2 free basis.                                         .sup.3 Assumed a carbon number of 4 for other oxygenates.                     .sup.4 Water is calculated as weight percent of the liquid phase.        

Although the invention has been described in considerable detail, itmust be understood that such detail is for the purpose of illustrationonly and that many variations and modifications can be made by oneskilled in the art without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A process for making alcohols comprisingcontacting a mixture of hydrogen and carbon monoxide with a catalystcomprising:(1) as a first component, at least one element selected fromthe group consisting of molybdenum and tungsten in free or combinedform; (2) as a second component, at least one element selected from thegroup consisting of cobalt and nickel in free or combined form; (3) as athird component, a promoter comprising an alkali or alkaline earthelement in free or combined form;said catalyst excluding rhodium andruthenium and containing less than two (2) weight percent copper; at apressure of at least about 500 psig and at conditions sufficient to forman alcohol fraction boiling in the range of motor gasoline in at least20 percent CO₂ free carbon selectivity, said alcohol fraction containinga C₁ to C₂₋₅ alcohol weight ratio of less than about 1:1.
 2. The processof claim 1 wherein the mixture of hydrogen and carbon monoxide containsa molar ratio of H₂ /CO of less than about 2:1.
 3. The process of claim1 wherein the alcohol fraction is formed in at least 50 percent CO₂ freecarbon selectivity.
 4. The process of claim 3 wherein the alcoholfraction contains a C₁ to C₂ -C₅ alcohol weight ratio of less than about0.8:1.
 5. The process of claim 4 wherein the alcohol fraction contains aC₁ to C₂ -C₅ alcohol weight ratio of less than about 0.5:1.
 6. Theprocess of claim 3 wherein the atomic ratio of the first component tothe second component is from about 1:4 to about 4:1.
 7. The process ofclaim 6 wherein the atomic ratio of the first component is from about3:1 to about 1:1.
 8. The process of claim 4 wherein the first and secondcomponents are molybdenum and cobalt respectively in free or combinedform.
 9. The process of claim 8 wherein the first and second componentsare present as coprecipitated sulfides.
 10. A process for makingalcohols comprising contacting a mixture of hydrogen and carbon monoxidewith a catalyst comprising:(1) as a first component, at least oneelement selected from the group consisting of molybdenum and tungsten infree or combined form; (2) as a second component, at least one elementselected from the group consisting of cobalt and nickel in free orcombined form; (3) as a third component, a promoter comprising an alkalior alkaline earth element in free or combined form,said catalystexcluding rhodium, copper and ruthenium; at a pressure of at least about500 psig and at conditions sufficient to form an alcohol fractionboiling in the range of motor gasoline in at least 20 percent CO₂ freecarbon selectively, said alcohol fraction containing a C₁ to C₂₋₅alcohol weight ratio of less than about 1:1.
 11. A process for makingalcohols comprising contacting a mixture of hydrogen and carbon monoxidewith a catalyst consisting essentially of:(1) as a first component, atleast one element selected from the group consisting of molybdenum andtungsten in free or combined form; (2) as a second component, at leastone element selected from the group consisting of cobalt and nickel infree or combined form; (3) as a third component, a promoter comprisingan alkalli or alkaline earth element in free or combined form; andoptionally (4) as a fourth component, a support;said catalyst excludingrhodium, copper and ruthenium; at a pressure of at least about 500 psigand at conditions sufficient to form an alcohol fraction boiling in therange of motor gasoline in at least 20 percent CO₂ free carbonselectivity, said alcohol fraction containing a C₁ to C₂₋₅ alcoholweight ratio of less than about 1:1.
 12. The process of claim 10 whereina ratio of methanol to C₂ -C₅ alcohols is lower than the process inwhich all the conditions are the same except that the catalyst does notcontain the second component.
 13. The process of claim 10 whereinchromium, manganese and zinc are excluded from the catalyst.
 14. Theprocess of claim 13 wherein halogen, titanium, vanadium, cerium,thorium, uranium, iridium, palladium, platinum, silver and cadmium areexcluded from the catalyst.